Soil imaging probe and method of processing soil image to detect hydrocarbon contamination

ABSTRACT

A soil imaging probe has a housing with an interior cavity and an outer surface exposed for sliding contact with soil. A window is mounted in the outer surface for providing optical communication between the soil and the interior cavity. An optical module is positioned within the interior cavity. The optical module includes at least one light source and a camera mounted in a block. An indexing surface is defined in the interior cavity to maintain the optical module at a predetermined fixed distance from the window to keep the camera focused on the soil outside the window. An elastomeric fill material fills the interior cavity and substantially surrounds the optical module to reduce energy transference from the housing of the probe to the optical module. An image processing method is also provided to identify pixels in an image captured by the camera that show potential hydrocarbon contamination.

RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.15/269,159 filed on Sep. 19, 2016, now U.S. Pat. No. 10,371,637, whichclaims the benefit of U.S. Provisional Patent Application No. 62/220,644filed on Sep. 18, 2015. The entire contents of these relatedapplications are incorporated herein by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates generally to devices and methods forimaging and measuring contaminants in soil. In particular, the presentinvention relates to devices and methods for imaging and measuringcontaminants in a bore hole using a camera mounted in a soil probe.

Description of the Related Art

Soil contamination is caused by the presence of chemicals, such ashydrocarbons, in the natural soil environment. Soil contamination cancause health risks from direct contact with the contaminated soil,vapors from the contaminants, and secondary contamination of watersupplies within and underlying the soil.

Soil probing tools are commonly used for subsurface soil investigationsto determine the presence and concentration of soil contaminants. Forexample, probing tools have been used to explore sites for hydrocarboncontamination in the soil.

Systems have been developed for logging soil properties in boreholes asprobing tools are driven into or retracted from the ground. For example,U.S. Pat. No. 5,639,956 issued to Christy discloses a soil probe havinga permeable membrane sensor disposed in the sidewall of the probe forsampling chemical compounds at different soil levels. Other types ofsensors have also been placed on soil probes to measure and logproperties of the soil at various levels as the probe is driven into orretracted from the soil.

Another example of a system for logging soil properties in a boreholeusing an imaging system is disclosed in U.S. Pat. Nos. 6,115,061 and6,630,947 of Lieberman. Lieberman uses visible or UV light from a lightsource to illuminate the soil in the borehole, and a lens arrangementand imaging system for detecting light reflected back from the soil.

PCT Patent Application No. WO 2005/003728 of Rooney et al. discloses asoil probe with a light source for illuminating the soil in situ. Thelight source is cycled between multiple wavelengths for the colors red,blue and green, in succession. A photo-detector responsive to light ofthe various wavelengths is used to measure the color of the soil as anR-G-B measurement. Soil parameters are obtained by correlation with thesoil color measurement.

U.S. Pat. No. 5,548,115 issued to Ballard et al. discloses a probedevice for in-situ detection of contaminants in subsurface soil. Thedevice uses UV light through a sapphire window to fluoresce contaminantsin the soil.

U.S. Pat. No. 5,128,882 issued to Cooper discloses a soil probe formeasuring reflectance and fluorescence of soil in situ. Reflected lightis transmitted through a fiber optic link to the surface for measurementof spectral distribution and intensity.

There is a need in the industry for an improved soil imaging probe andmethod that uses a camera mounted in a soil probe to image and measuresubsurface soil contaminants.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a soil imaging probethat can be assembled in an efficient and economical manner.

A further object of the present invention is to provide a soil imagingprobe that is configured in a manner to withstand percussion advancementof the probe.

A still further object of the present invention is to provide a soilimaging method that uses a two stage image filtering process to detecthydrocarbon contamination in the soil with reduced background detection.

These and other objects of the present invention are accomplished by asoil imaging probe having a housing with an interior cavity and an outersurface exposed for sliding contact with soil. A window is mounted inthe outer surface for providing optical communication between the soiland the interior cavity. An optical module is positioned within theinterior cavity. The optical module includes at least one light sourceand a camera mounted in a block. An indexing surface is defined in theinterior cavity to maintain the optical module at a predetermined fixeddistance from the window to keep the camera focused on the soil outsidethe window and properly aligned with the probe. An elastomeric fillmaterial fills the interior cavity and substantially surrounds theoptical module to reduce energy transference from the housing of theprobe to the optical module. An image processing method is also providedto identify pixels in an image captured by the camera that showpotential hydrocarbon contamination.

According to one aspect of the present invention, a soil imaging methodis provided, comprising: acquiring an image of soil in a bore hole usinga soil imaging probe having a window for providing optical communicationbetween the soil and a camera positioned within the soil imaging probe;and processing the image to identify pixels in the image that showpotential hydrocarbon contamination. The image processing comprisesapplying a first stage filter to the pixels that uses a first set ofimage parameters to assign a first fluorescence value to each pixelindicative of hydrocarbon contamination.

According to other aspects of the invention, the image processingfurther includes: applying a second stage filter to the pixels that usesa second set of image parameters to assign a second fluorescence valueto each pixel indicative of hydrocarbon contamination; determining ifthe first stage filter detects fluorescence indicative of hydrocarboncontamination in at least a predetermined percentage of area of theimage; and summing the first and second fluorescence values for use invisually rendering an image showing hydrocarbon contamination or forquantitatively describing a level of hydrocarbon contamination upondetermining that the first stage filter detects fluorescence indicativeof hydrocarbon contamination in at least the predetermined percentage ofarea of the image.

According to another aspect of the present invention, a soil imagingmethod is provided, comprising: acquiring an image of soil in a borehole using a soil imaging probe having a window for providing opticalcommunication between the soil and a camera positioned within the soilimaging probe; and processing the image to determine a percentage ofarea of the image that has fluorescence indicative of hydrocarboncontamination.

Numerous other objects of the present invention will be apparent tothose skilled in this art from the following description wherein thereis shown and described embodiments of the present invention, simply byway of illustration of some of the modes best suited to carry out theinvention. As will be realized, the invention is capable of otherdifferent embodiments, and its several details are capable ofmodification in various obvious aspects without departing from theinvention. Accordingly, the drawings and description should be regardedas illustrative in nature and not restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more clearly appreciated as thedisclosure of the present invention is made with reference to theaccompanying drawings. In the drawings:

FIG. 1 is a perspective front view of a soil imaging probe according tothe present invention.

FIG. 2 is a perspective rear view of the soil imaging probe.

FIG. 3 is an exploded perspective front view of the soil imaging probe.

FIG. 4 is an exploded perspective rear view of the soil imaging probe.

FIG. 5 is another exploded perspective rear view of the soil imagingprobe.

FIG. 6 is a cross section side view of the soil imaging probe.

FIG. 7 is another cross section side view of the soil imaging probeshowing an elastomeric fill material contained within an interior cavityof the probe.

FIG. 8 is a flow chart showing a soil imaging method of the presentinvention that uses a two-stage filtering process to determinefluorescence indicative of soil contamination.

FIG. 9 shows a raw image of typical uncontaminated soil in a bore hole.

FIG. 10 shows a raw image of contaminated soil in a bore hole.

FIG. 11 shows a rendered image of the soil shown in FIG. 10, with thepixels passing a first stage filter shown in red.

FIG. 12 shows a rendered image of the soil shown in FIG. 10, with thepixels passing a second stage filter shown in yellow.

DETAILED DESCRIPTION OF THE INVENTION

A soil imaging probe 10 and soil imaging method according to the presentinvention will be described in detail with reference to FIGS. 1 to 12 ofthe accompanying drawings.

FIGS. 1 to 7 illustrate the soil imaging probe 10 of the presentinvention. The soil imaging probe 10 includes a housing 11 having alongitudinal axis and an outer surface 12 exposed for sliding contactwith soil as the housing 11 is moved through the soil along itslongitudinal axis. The housing 11 has an interior cavity 13. An accessopening 14 is provided in a back side 15 of the housing 11, and anaccess cover 16 is provided to close the access opening 14 and seal theinterior cavity 13. The access cover 16 is removable from the housing 11to allow access through the access opening 14 to the interior cavity 13.

A window 17 is mounted in an opening 18 in the outer surface of a frontside 19 of the housing 11 for providing optical communication betweenthe soil and the interior cavity 13. The window 17 is preferably mountedflush with the exterior surface 12 of the probe 10 and made of a hardmaterial, such as sapphire, to resist scratching as the probe 10 isdriven into the soil. The window 17 is on the opposite side of thehousing 11 from the access cover 16.

An optical module 20 is positioned within the interior cavity 13 of thehousing 11. The optical module 20 includes a block 21, a pair of lightsources 22, 23 mounted in the block 21, and a camera 24 mounted in theblock 21. Also affixed to the block 21 are electrical components andelectrical connections for the light sources 22, 23 and the camera 24and other sensors (if any) contained within the probe 10. All of thesecomponents 22-24 are rigidly attached to the block 21. Electrical wiresand gas lines (if used) can exit the block 21 as a single trunkline 25,which is directed out the top of the probe 10.

The block 21 is made of a rigid, lightweight material, such as aluminumor plastic. For example, the block 21 can be made of nylon, PVC, or ABS.

The light sources 22, 23 include a first light source 22 for emittinglight having a first wavelength, and a second light source 23 foremitting light having a second wavelength different from the firstwavelength. In one embodiment, the first light source 22 is a UV lightsource, and the second light source 23 is a visible light source.

The two light sources 22, 23 are fixed in respective bores 26, 27 in theblock 21 that extend at an angle relative to each other and converge ata focal point located approximately at the external surface of thewindow 17. The camera 24 is fixed in a center bore 24 b in the block 21between the two light sources 22, 23 and aimed at the focal point.

During use, light is directed from the light sources 22, 23 to the soilthrough the window 17. Returning light from the soil returns backthrough the window 17 to the camera 24. The images captured by thecamera 24 using this probe 10 can be either video or still. Imagesilluminated with visible light are used to view the soil present at theprobe window 17. Images illuminated with UV light are used to detect thepresence of certain hydrocarbon fuels that will fluoresce when exposedto UV excitation in the appropriate wavelengths. Images obtained with UVlight are subjected to image processing, as described in detail below,to indicate the degree of fluorescence present in the soil and toseparate hydrocarbon fluorescence from background mineral fluorescence.

An indexing surface 28 is provided on a front wall of the interiorcavity 13. The indexing surface 28 is a planar surface that lies in aplane parallel to the longitudinal axis of the probe 10. The indexingsurface 28 can be formed, for example, by machining the front wall ofthe interior cavity 13 through the access opening 14 so that a precisedistance is created from the indexing surface 28 to the exterior surfaceof the window 17. The indexing surface 28 functions to maintain theoptical module 20 at a predetermined fixed distance from the exteriorsurface of the window 17 to keep the camera 24 focused on the soilcontacting the outside of the window 17 and properly aligned with theprobe 10.

An elastomeric gasket 29 is positioned between the block 21 and theindexing surface 28 to isolate the optical module 20 from energytransference from the housing 11 to the optical module 20. For example,the elastomeric gasket 29 can be a of elastomeric material having ahardness of approximately Shore 30A, such as ⅛ inch thick silicone.

As illustrated in FIGS. 5 and 6, the interior cavity 13 of the housing11 is substantially longer than a longitudinal dimension of the block 21of the optical module 20. For example, in the illustrated embodiment,the interior cavity 13 is more than 1.5 times as long as thelongitudinal dimension of the block 21.

As illustrated in FIG. 7, an elastomeric fill material 30 fills theinterior cavity 13 of the housing 11 and substantially surrounds theoptical module 20, except for the front side of the optical module 20facing the indexing surface 28. The elastomeric fill material 30functions to reduce energy transference from the housing 11 of the probe10 to the optical module 20. Since the interior cavity 13 of the housing11 is substantially longer than the optical module 20, the elastomericfill material 30 effectively isolates the optical module 20 from thehousing 11 of the probe 10 in a longitudinal direction. Thus, theelastomeric fill material 30 effectively isolates the optical module 20from the severe energy forces imparted to the housing 11 in alongitudinal direction while driving the probe 10 into the soil.

The probe 10 is assembled by affixing the block 21 of the optical module20 to the gasket 29, and the gasket 29 to the interior indexing surface28 with a contact adhesive or other adhesive. Alternatively, no adhesivemay be used and the block 21 and gasket 29 may be held against theinterior indexing surface 28 by a temporary mechanical fastener insertedthrough the window opening 18.

The access cover 16 is secured to the housing using, for example, aplurality of threaded fasteners 31. The interior cavity 13 is thenfilled with an elastomeric fill material 30 initially in liquid form,such as silicone or polyurethane, that contacts and substantiallysurrounds the optical module 20 within the interior cavity 13. Theelastomeric fill material 30 does not completely surround the opticalmodule 20 because it does not reach the front side of the optical module20, which is held against the gasket 29 and the indexing surface 28during assembly to maintain the desired focal point for the camera 24 onthe exterior surface of the window 17.

Once the elastomeric fill material 30 cures into its solid form, theoptical module 20 is held in place against the indexing surface 28 bythe elastomeric fill material 30 and can be released from its temporaryhold through the window opening 18. The optical module 20 is thus heldin place within the interior cavity 13 only by the elastomeric fillmaterial 30 and without the use of any rigid mechanical fastening. Inother words, the optical module 20 is free floating within theelastomeric fill material 30 in the interior cavity 13. The elastomericfill material 30 cushions the optical module 20 and prevents percussiveenergy used to drive the probe 10 into the soil from damaging thecomponents 20-23 of the optical module 20. Within the confines of theelastomeric fill material 30, the optical block 20 is free to moverelative to the indexing surface 28 in a longitudinal direction.

The soil imaging probe 10 described above allows the camera 24, lightsources 22, 23, and other electronic components to be fixed to a singlerigid block 21 of lightweight material. This block 21 can be placed inthe interior cavity 13 of the probe housing 11 through the accessopening 14, indexed to the window 17 of the probe 10 by the indexingsurface 28, and held in place with the elastomeric fill material 30.Within the elastomeric fill material 30, the block 21 is free floating,not being fixed to the probe 10 with any rigid mechanical fastening.

A soil image processing method according to the present invention willnow be described with reference to FIGS. 8 to 12. The soil imageprocessing method can be used to indicate the degree of fluorescencepresent in the soil and to separate hydrocarbon fluorescence frombackground mineral fluorescence.

FIG. 8 is a flow chart of the soil imaging method used to determinefluorescence indicative of soil contamination. An image of soil in abore hole is acquired using a soil imaging probe having a window forproviding optical communication between the soil and a camera positionedwithin the soil imaging probe. For example, the soil imaging probe 10described above can be used to acquire the soil images used in this soilimage processing method.

The soil imaging probe 10 is used to acquire digital camera images ofsoil under UV illumination at fixed increments (e.g., 0.05 ft) as theprobe 10 is advanced in the soil. These camera images are then analyzedto determine what area of the image emits light indicative ofhydrocarbon fuel fluorescence. More specifically, each acquired digitalcamera image is processed to identify pixels in the image that showpotential hydrocarbon contamination. The result of the image processingis used to generate a fluorescence value for use in visually renderingan image showing hydrocarbon contamination, or for quantitativelydescribing a level of hydrocarbon contamination.

The image processing uses a two stage filtering process designed toidentify hydrocarbon contamination signals and to separate those signalsfrom background soil fluorescence and reflectance. In this filteringprocess, Hue, Saturation, and Value (HSV) color filters are applied toeach pixel in the soil image. Pixels that indicate positive forfluorescence in this analysis can then be represented either through avisually rendered image or quantitatively described by the percent areaof the image. The quantitative description can also use a factor for theintensity of light in the area of fluorescence.

The image processing applies a first stage filter to the pixels using afirst set of image parameters to assign a first fluorescence value toeach pixel indicative of hydrocarbon contamination. The first stagefilter identifies pixels having a Hue range and a first brightness Valuerange indicative of hydrocarbon fluorescence, and having a firstSaturation range. The first stage filter is set to identify pixels thatare high in color in the Hue range typical of hydrocarbon fluorescenceand are of sufficient brightness to indicate hydrocarbon contamination.The first stage filter does not detect high concentrated areas ofproduct near the center of a fluorescent image. For example, the firststage filter can be set to identify pixels having a Hue range ofapproximately 150 to 220, a Saturation range of approximately 127 to255, and a brightness Value range of approximately 105 to 255.

The image processing applies a second stage filter to the pixels using asecond set of image parameters to assign a second fluorescence value toeach pixel indicative of hydrocarbon contamination. The second stagefilter identifies image pixels low in color and high in brightness; acondition typical of high fluorescence in certain hydrocarbons, as wellas a condition found at the center of many images with strongfluorescence values identified by the first stage filter. The secondstage filter identifies pixels having, for example, the same Hue rangeas the first stage filter, a second brightness Value range, and a secondSaturation range. The second brightness Value range has a lower limitthat is higher than a lower limit of the first brightness Value range.The second Saturation range is lower than the first Saturation range.For example, the second stage filter can be set to identify pixelshaving a Hue range of approximately 150 to 220, a Saturation range ofapproximately 0 to 127, and a brightness Value range of approximately150 to 255.

The second stage filter uses Saturation levels below a lower limit ofthe first stage filter to detect hydrocarbon contamination indicated byfluorescent light of low color and high brightness. This condition oftenoccurs in soil images made in zones with high hydrocarbon concentrationsand most often is found near the center of soil images. The second stagefilter uses brightness Values above a lower limit of the first stagefilter to decrease background detection caused by low Saturationparameter limits.

The image processing determines if the first stage filter detectsfluorescence indicative of hydrocarbon contamination in at least apredetermined percentage of area of the image. For example, thepredetermined percentage can be approximately 20% of the area of theimage.

If the first stage filter detects fluorescence indicative of hydrocarboncontamination in less than the predetermined percentage of area of theimage, then the first fluorescence value is output for use in visuallyrendering an image showing hydrocarbon contamination, or for use inquantitatively describing the level of hydrocarbon contamination.

If the first stage filter detects fluorescence indicative of hydrocarboncontamination in more than the predetermined percentage of area of theimage, then the first fluorescence value is summed with the secondfluorescence value for use in visually rendering an image showinghydrocarbon contamination, or for use in quantitatively describing thelevel of hydrocarbon contamination. The second fluorescence value isonly summed with the first fluorescence value if the first stage filterdetects fluorescence in at least the predetermined percentage of theimage to avoid background detections from soil minerals having lowcolor.

The fluorescence value output by the image processing algorithm is usedto display a quantitative description of a level of hydrocarboncontamination based on the percentage of area of the image determined tohave fluorescence indicative of hydrocarbon contamination. Thequantitative description can include a factor for the intensity of lightin a fluorescing area of the image.

The fluorescence value output by the image processing algorithm can alsobe used to render a visual image to show detected hydrocarboncontamination. The rendered image includes a visual indication ofhydrocarbon contamination for each pixel in the image. The visualindication is based only on the first fluorescence value when the firststage filter detects fluorescence in less than the predeterminedpercentage of area of the image, and is based on the sum of the firstand second fluorescence values when the first stage filter detectsfluorescence in more than the predetermined percentage of area of theimage.

FIGS. 9 to 12 further illustrate the image analysis process used in thepresent invention. FIGS. 9 and 10 show raw images of soil obtained atdifferent depths within the same bore hole. FIGS. 11 and 12 show imageswith rendered pixels from the image analysis process.

FIG. 9 shows a raw image of soil from a first depth in the bore hole.This image is typical of background, uncontaminated, soils. The imageexhibits low fluorescence and yields a fluorescence value ofapproximately 0% from the image analysis process.

FIG. 10 shows another raw image of soil from a second depth in the borehole. This image was obtained in a hydrocarbon contaminated zone andcontains visually discernible hydrocarbon fluorescence.

FIG. 11 shows a rendered image of the soil shown in FIG. 10, with thepixels passing the first stage filter shown in red. The total areapassing the first stage filter is approximately 29.7% in this image.

The image from FIG. 11 has sufficient fluorescent area identified by thefirst stage filter to use the fluorescence value output from the secondstage filter. Pixels passing the second stage filter are shown in yellowin FIG. 12. The area passing the second stage filter is approximately36.2% in this image. This area is summed to the area detected by thefirst stage filter to yield a fluorescence area value of approximately65.9% for this image.

Filter parameters for the first and second stage filters of the imageprocessing can be determined through test comparisons of soils with andwithout hydrocarbon contamination. For example, several sample soiltypes can be contaminated with known quantities of hydrocarbons andcompared to non-contaminated control samples. Hue parameters can bedetermined by examining fluorescence of several types of hydrocarbons atlow concentrations up to free product concentrations. Hue can beselected to span just beyond the maximum and minimum limits of thefluorescent Hues detected in the samples. Saturation and Valueparameters can be set based on the comparisons of the images of thecontaminated soils and the uncontaminated control soils.

The parameters for the first and second stage filters are set such as tominimize background detection while maximizing detection of hydrocarboncontamination. The parameters for the second stage filter are selectedbased on free product tests. Free product near the focus of the cameraimage produces high fluorescence of light with Saturation levels belowthe first stage filter detection limits. The Value parameters of thesecond stage filter are set sufficiently high to exclude backgrounddetection that could be caused by soil reflection or fluorescence ofsoil minerals.

The image analysis process described above applies both the first andsecond stage filters to each pixel of an image before determiningwhether the first stage filter detects fluorescence in at least thepredetermined percentage of area of the image. However, it will beappreciated that the image analysis process could be modified so thatthe second stage filter is only applied to the pixels in an image if thefirst stage filter detects fluorescence in at least the predeterminedpercentage of area of the image. In this modified process, thefluorescence value output from the image analysis process would be thesame as in the process described above and shown in FIG. 8, the onlydifference being that the second stage filter would only be applied tothe pixels in an image if the threshold level of fluorescence is firstdetected by the first stage filter.

While the invention has been described in connection with specificembodiments thereof, it is to be understood that this is by way ofillustration and not of limitation, and the scope of the appended claimsshould be construed as broadly as the prior art will permit.

What is claimed is:
 1. A soil imaging method, comprising: acquiring adigital camera image of soil in a bore hole using a soil imaging probehaving a window for providing optical communication between the soil anda camera positioned within said soil imaging probe, said digital cameraimage comprising a plurality of pixels; and processing said digitalcamera image to identify pixels in the digital camera image that showpotential hydrocarbon contamination, wherein said image processingcomprises applying a first stage filter to each of said pixels that usesa first set of image parameters to assign a first fluorescence value toeach pixel indicative of hydrocarbon contamination.
 2. The soil imagingmethod according to claim 1, wherein said image processing furthercomprises using the first fluorescence value in visually rendering animage showing hydrocarbon contamination or for quantitatively describinga level of hydrocarbon contamination.
 3. The soil imaging methodaccording to claim 1, wherein said image processing further comprisesapplying a second stage filter to said pixels that uses a second set ofimage parameters to assign a second fluorescence value to each pixelindicative of hydrocarbon contamination.
 4. The soil imaging methodaccording to claim 3, wherein said image processing further comprisesdetermining if the first stage filter detects fluorescence indicative ofhydrocarbon contamination in at least a predetermined percentage of areaof the image.
 5. The soil imaging method according to claim 1, furthercomprising rendering a visual image based on said image processing toshow detected hydrocarbon contamination.
 6. The soil imaging methodaccording to claim 5, wherein said rendered image includes a visualindication of hydrocarbon contamination for each pixel.
 7. The soilimaging method according to claim 6, wherein said visual indication isbased on said first fluorescence value when said first stage filterdetects fluorescence in less than said predetermined percentage of areaof the image.
 8. The soil imaging method according to claim 3, furthercomprising rendering a visual image based on said image processing toshow detected hydrocarbon contamination, wherein said rendered imageincludes a visual indication of hydrocarbon contamination for eachpixel, wherein said visual indication is based on said firstfluorescence value when said first stage filter detects fluorescence inless than said predetermined percentage of area of the image, andwherein said visual indication is based on the sum of said first andsecond fluorescence values when said first stage filter detectsfluorescence in more than said predetermined percentage of area of theimage.
 9. The soil imaging method according to claim 1, furthercomprising displaying a quantitative description of a level ofhydrocarbon contamination based on a percentage of area of the imagedetermined to have fluorescence indicative of hydrocarbon contamination.10. The soil imaging method according to claim 9, wherein saidquantitative description includes a factor for the intensity of light ina fluorescing area of the image.
 11. The soil imaging method accordingto claim 3, wherein said second stage filter uses Saturation levelsbelow a lower limit of said first stage filter to detect free producthydrocarbon contamination near a focus of the camera image.
 12. The soilimaging method according to claim 3, wherein said second stage filteruses brightness Values above a lower limit of said first stage filter todecrease background detection caused by low Saturation parameter limits.13. A soil imaging method, comprising: acquiring an image of soil in abore hole using a soil imaging probe having a window for providingoptical communication between the soil and a camera positioned withinsaid soil imaging probe; and processing said image to identify pixels inthe image that show potential hydrocarbon contamination, wherein saidimage processing comprises applying a first stage filter to said pixelsthat uses a first set of image parameters to assign a first fluorescencevalue to each pixel indicative of hydrocarbon contamination; whereinsaid image processing further comprises applying a second stage filterto said pixels that uses a second set of image parameters to assign asecond fluorescence value to each pixel indicative of hydrocarboncontamination; wherein said image processing further comprisesdetermining if the first stage filter detects fluorescence indicative ofhydrocarbon contamination in at least a predetermined percentage of areaof the image; wherein said image processing further comprises summingthe first and second fluorescence values for use in visually renderingan image showing hydrocarbon contamination or for quantitativelydescribing a level of hydrocarbon contamination upon determining thatthe first stage filter detects fluorescence indicative of hydrocarboncontamination in at least said predetermined percentage of area of theimage.
 14. The soil imaging method according to claim 13, wherein saidsecond fluorescence value is only summed with said first fluorescencevalue if the first stage filter detects fluorescence in at least saidpredetermined percentage of the image to avoid background detectionsfrom soil minerals having low color.
 15. A soil imaging method,comprising: acquiring an image of soil in a bore hole using a soilimaging probe having a window for providing optical communicationbetween the soil and a camera positioned within said soil imaging probe;and processing said image to identify pixels in the image that showpotential hydrocarbon contamination, wherein said image processingcomprises applying a first stage filter to said pixels that uses a firstset of image parameters to assign a first fluorescence value to eachpixel indicative of hydrocarbon contamination; wherein said imageprocessing further comprises applying a second stage filter to saidpixels that uses a second set of image parameters to assign a secondfluorescence value to each pixel indicative of hydrocarboncontamination; and wherein said first stage filter identifies pixelshaving a Hue range and a first brightness Value range indicative ofhydrocarbon fluorescence, and having a first Saturation range.
 16. Thesoil imaging method according to claim 15, wherein said second stagefilter identifies pixels having said Hue range, a second brightnessValue range, and a second Saturation range.
 17. The soil imaging methodaccording to claim 16, wherein said second brightness Value range has alower limit that is higher than a lower limit of said first brightnessValue range, and said second Saturation range is lower than said firstSaturation range.
 18. The soil imaging method according to claim 16,wherein said first stage filter identifies pixels having a Hue range ofapproximately 150 to
 220. 19. The soil imaging method according to claim16, wherein said first stage filter identifies pixels having aSaturation range of approximately 127 to
 255. 20. The soil imagingmethod according to claim 16, wherein said first stage filter identifiespixels having a brightness Value range of approximately 105 to
 255. 21.The soil imaging method according to claim 16, wherein said second stagefilter identifies pixels having a Hue range of approximately 150 to 220.22. The soil imaging method according to claim 16, wherein said secondstage filter identifies pixels having a Saturation range ofapproximately 0 to
 127. 23. The soil imaging method according to claim16, wherein said second stage filter identifies pixels having abrightness Value range of approximately 150 to 255.